JP2692918B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, wherein when forming a tungsten layer covering a contact hole, it is possible to make it difficult for a hollow to enter the tungsten layer.
Manufacturing a semiconductor device capable of making a substrate in a contact hole difficult to be etched when a tungsten layer is embedded in the contact hole and making good contact in the contact hole to improve device characteristics For the purpose of providing a method, a step of forming an insulating film so as to have a contact hole on a substrate, and a growth rate for tungsten more than for the substrate so as to cover the inside of the contact hole and the insulating film by a sputtering method. Forming a slow metal layer, and anisotropically etching the metal layer to selectively etch the metal layer to expose the substrate in the contact hole, and the metal layer on the sidewall of the insulating film in the contact hole. Exposed and exposed in the contact hole by chemical vapor deposition A step of forming a tungsten layer so as to cover the substrate and the metal layer formed by etching, and a step of etching the tungsten layer on the metal layer other than the contact hole to leave the tungsten layer only in the contact hole. And a step of forming a wiring layer so as to make a contact with the tungsten layer left in the contact hole.

[Industrial applications]

The present invention relates to a method for manufacturing a semiconductor device, and can be applied to the formation of a contact between a wiring layer and a substrate diffusion layer of, for example, an emitter, a collector, and a source in a contact hole. The present invention relates to a method for manufacturing a semiconductor device, which enables good contact between a diffusion layer and a wiring layer.

For example, in a semiconductor device such as a bipolar transistor, there is a technique in which the contact hole is filled with a wiring layer made of metal in order to make contact with the substrate diffusion layer in the contact hole that constitutes the semiconductor device. There are two known methods of burying the wiring layer in the contact hole. Specifically, there is a method of selectively burying the wiring layer only in the contact hole by a chemical vapor deposition (CVD) method. In this method, a wiring layer is formed over the entire surface by CVD so as to cover the contact hole, and then etched back to fill the contact hole. The present invention relates to this latter method.

[Conventional technology]

 Hereinafter, the related art will be described.

3A to 3E are views for explaining a conventional method for manufacturing a semiconductor device. The manufacturing method of the semiconductor device of the illustrated example can be applied to the manufacturing method of a semiconductor device such as a bipolar transistor.

In this figure, 21 is a substrate made of Si and 22 is, for example, Si.
An insulating film made of O ₂ , 23 is a contact hole, 24 is a metal layer made of Ti (may be a metal nitride film such as W, TiW, TiN, WN, etc.), and 25 is a tungsten (W) layer that functions as a wiring. , 26 are wiring layers made of Al.

 Next, the manufacturing process will be described.

First, as shown in FIG. 3 (a), SiO ₂ is deposited on the substrate 21 by, for example, the CVD method to form the insulating film 22, and then the insulating film 22 is selectively etched by, for example, the RIE method to make contact. The hole 23 is formed.

Next, as shown in FIG. 3B, Ti is deposited by a sputtering method so as to cover the inside of the contact hole 23 and the insulating film 22 to form a metal layer 24.

Here, the metal layer 24 is formed between the insulating film 22 made of SiO ₂ and the tungsten layer 25 is the insulating film made of SiO _2.
This is to prevent the adhesion between 22 and the tungsten layer 25 formed by the CVD method from being poor and to improve the adhesion. Specifically, since the metal layer 24 is formed on the insulating film 22 by the sputtering method, the adhesion between the insulating film 22 and the metal layer 24 is good, and the adhesion between the metal layer 24 and the tungsten layer 25 is also good. Since it is good, the adhesion between the insulating film 22 and the tungsten layer is improved through the metal layer 24. Therefore, the metal layer 24 here functions as an adhesion film to the insulating film 22 and the tungsten layer 25.

Next, as shown in FIG. 3C, a tungsten layer 25 is formed so as to cover the metal layer 24 by the CVD method.

Next, as shown in FIG. 3D, the tungsten layer 25
Is etched back to fill the tungsten layer 25 in the contact hole 23.

Then, as shown in FIG. 3 (e), Al is deposited by a sputtering method so as to make contact with the tungsten layer 25 to form a wiring layer 26. It should be noted that a substrate diffusion layer (not shown) is usually formed on the substrate 21 in the contact hole 23 by ion implantation and annealing heat treatment after forming the contact hole 23 shown in FIG.

[Problems to be solved by the invention]

However, in such a conventional semiconductor device manufacturing method, the contact hole 23
Must be formed small (aspect ratio is 1 or more), and when the step difference in the contact hole 23 becomes severe accordingly (specifically, the diameter of the contact hole 23 is small and the height of the contact hole 23 is high). As shown in FIG. 4 (a), when forming the tungsten layer 25 so as to cover the contact hole 23, the tungsten layer 25 is hollow (X portion shown in FIG. 4 (a), so-called "su"). Will enter. Therefore, as shown in FIG. 4B, when the tungsten layer 25 is etched back to fill the tungsten layer 25 in the contact hole 23, the substrate 21 in the contact hole 23 is easily etched. . This tends to become more remarkable as the size is reduced. The substrate 21 in the contact hole 23 is easily etched because the etch back of the tungsten layer 25 is caused by the insulating film of the tungsten layer 25.
22 is determined by the thickness of the upper portion (Y portion shown in FIG. 4 (a)), but the thickness below the hollow portion formed in the tungsten layer 25 (Z portion shown in FIG. 4 (a)) depends on the hollow portion. It is caused by the fact that the thickness becomes insufficient with respect to the above thickness (Y portion) due to the formation. Therefore, the substrate diffusion layer formed on the substrate 21 in the contact hole 23 is also etched, resulting in contact failure and deteriorating the device characteristics.

Therefore, according to the present invention, when forming the tungsten layer covering the contact hole, it is possible to make it difficult for the hollow space to enter the tungsten layer. When the tungsten layer is etched and embedded in the contact hole, the substrate in the contact hole is etched. It is an object of the present invention to provide a method for manufacturing a semiconductor device which can be made difficult and can make good contact in a contact hole to improve device characteristics.

[Means for solving the problem]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises a step of forming an insulating film on a substrate so as to have a contact hole, and a step of covering the inside of the contact hole and the insulating film by a sputtering method. Forming a metal layer having a slower growth rate with respect to tungsten, and selectively exposing the metal layer by anisotropic etching to expose the substrate in the contact hole, and the insulating layer in the contact hole. Leaving the metal layer on the side wall of the film, and forming a tungsten layer so as to cover the substrate and the metal layer exposed in the contact hole by chemical vapor deposition.
Etching the tungsten layer on the metal layer other than the contact hole to leave the tungsten layer only in the contact hole; and wiring to make contact with the tungsten layer left in the contact hole. And a step of forming a layer.

[Action]

According to the present invention, after an insulating film is formed on a substrate so as to have a contact hole, and a metal layer having a slower growth rate for tungsten than that of the substrate is formed by a sputtering method so as to cover the inside of the contact hole and the insulating film. The metal layer is selectively etched by anisotropic etching to expose the substrate in the contact hole and leave the metal layer on the side wall of the insulating film in the contact hole. Then, a tungsten layer is formed by chemical vapor deposition so as to cover the exposed substrate and metal layer, and the tungsten layer on the metal layer other than the contact hole is etched and left only in the contact hole. That is, the tungsten layer on the metal layer is etched back to fill the contact hole with the tungsten layer. afterwards,
A wiring layer is formed so as to make contact with the tungsten layer embedded in the contact hole.

Therefore, when the tungsten layer 25 is formed to cover the contact hole 23 by the CVD method as shown in FIG. 1D, tungsten grows on the substrate 21 made of Si as shown in FIG. Growth rate (A part) and growth rate on the metal layer 24 formed by the sputtering method (B part)
And the growth rate for growing on the substrate 21 made of Si is higher. Therefore, when the tungsten layer 25 is formed so as to cover the contact hole 23, the exposed portion of the substrate 21 in the contact hole 23 (A in FIG. 2) is in the lateral direction of the metal layer 24 in the contact hole 23. (B
Part)), the growth rate is higher than that of the contact hole, so that the tungsten layer 25 can be made less likely to be hollow. As shown in FIG. 1 (e), the tungsten layer 25 is etched back to form a contact hole. Since the tungsten layer 25 can be formed thick on the exposed substrate 21 when the substrate 21 is embedded in the contact hole 23, the substrate 21 in the contact hole 23 can be made difficult to be etched. Then, the substrate diffusion layer formed in the contact hole 23 can be made difficult to be etched, and the contact in the contact hole 23 can be favorably made to improve the device characteristics.

〔Example〕

 Hereinafter, the present invention will be described with reference to the drawings.

1 and 2 are views for explaining an embodiment of the method for manufacturing a semiconductor device according to the present invention, and FIGS.
(F) is a figure explaining the manufacturing process of one Example, and FIG. 2 is a figure explaining the effect of one Example.

In these figures, the same reference numerals as those in FIGS. 3 (a) to 3 (e) indicate the same or corresponding portions, and 1 is a resist film.

The metal layer 24 can function as an adhesion film with respect to the insulating film 22 and the tungsten layer 25.

 Next, the manufacturing process will be described.

First, as shown in FIG. 1A, SiO ₂ is deposited on the substrate 21 by, for example, the CVD method to form the insulating film 22 having a film thickness of, for example, 1 μm, and then the insulating film 22 is selected by, for example, the RIE method. To form a contact hole 23 having a diameter of, for example, 0.5φ. This corresponds to the step of forming the insulating film so as to have the contact hole on the substrate of the present invention.

Next, as shown in FIG. 1B, Ti is deposited by a sputtering method so as to cover the inside of the contact hole 23 and the insulating film 22 to form a metal layer 24 having a film thickness of, for example, 500 Å. This corresponds to the step of forming a metal layer having a slower growth rate for tungsten than the substrate so as to cover the contact hole and the insulating film by the sputtering method of the present invention.

Next, as shown in FIG. 1C, the resist film 1 is selectively formed on the metal layer 24, and the metal layer 24 is selectively etched by anisotropic etching using the resist film 1 as a mask. The substrate 21 is exposed in the contact hole 23 and the metal layer 24 is left on the sidewall of the insulating film 22 in the contact hole 23. This corresponds to the process of the present invention in which the metal layer is selectively etched by anisotropic etching to expose the substrate in the contact hole and leave the metal layer on the side wall of the insulating film in the contact hole.

Next, as shown in FIG. 1D, after removing the resist film 1, a tungsten layer 25 is formed by the CVD method so as to cover the substrate 21 and the metal layer 24 exposed in the contact hole. This corresponds to the step of forming the tungsten layer by the chemical vapor deposition method so as to cover the substrate and the metal layer exposed in the contact hole. Here
The reducing gas used in the CVD method is H ₂ gas or SiH ₄
Gas and the like, but since easily erode used when the substrate 21 of H ₂ gas used erosion hardly SiH ₄ gas substrate 21 preferred.

Next, as shown in FIG. 1 (e), the tungsten layer 25
Is etched back and embedded in the contact hole 23.
This corresponds to the step of etching the tungsten layer on the metal layer other than the contact hole and leaving the tungsten layer only in the contact hole of the present invention.

Then, as shown in FIG. 1 (f), contact is made with the tungsten layer 25 embedded by the CVD method.
Al is deposited to form the wiring layer 26. This corresponds to the step of forming the wiring layer so as to make contact with the tungsten layer left in the contact hole of the present invention. Note that the substrate 21 in the contact hole 23 is usually formed with a substrate diffusion layer by ion implantation and annealing heat treatment after forming the contact hole 23 shown in FIG.

That is, in the above-described embodiment, as shown in FIG. 1C, after exposing the substrate 21 in the contact hole 23 and leaving the metal layer 24 on the sidewall of the insulating film 22 in the contact hole 23, As shown in FIG. 1D, a tungsten layer 25 is formed by the CVD method so as to cover the substrate 21 and the metal layer 24 exposed in the contact hole 23. Here, when the tungsten layer 25 is formed to cover the contact hole 23 by the CVD method, as shown in FIG. 2, tungsten grows on the substrate 21 made of Si by the growth rate (A portion) and the sputtering method. The growth rate for growing on the formed metal layer 24 (section B) is different, and the growth rate for growing on the substrate 21 made of Si is higher.
Therefore, the contact hole 23 is covered with the tungsten layer.
When forming 25, the contact hole 23 is on the exposed substrate 21 in the contact hole 23 (A portion shown in FIG. 2).
Since the growth rate can be made larger and thicker than the lateral direction (B portion) of the metal layer 24 in the inside, it is possible to make it difficult for the tungsten layer 25 to have a hollow. And the tungsten layer
Since the tungsten layer 25 can be formed thick on the exposed substrate 21 when the etch back is performed on the substrate 25 in the contact hole 23, the substrate 21 in the contact hole 23 can be formed.
Can be made difficult to be etched. Therefore,
It is possible to prevent the substrate diffusion layer formed in the contact hole 23 from being easily etched, and to make good contact in the contact hole 23 to improve the device characteristics.

In the above embodiment, as shown in FIG. 1 (c), the substrate 21 is exposed in the contact hole 23, and the metal layer 24 is left on the side wall of the insulating film 22 in the contact hole 23. Although the case of forming 25 has been described, the present invention is not limited to this, the substrate 21 is exposed in the contact hole 23, and the metal layer 24 is left on the sidewall of the insulating film 22 in the contact hole 23. After that, the tungsten layer 25 may be formed by performing a dry treatment with a hydrofluoric acid (HF) vapor (or a wet treatment with a hydrofluoric acid solution), and in this case,
It is possible to make it more difficult for the hollow layer to enter the tungsten layer 25 as compared with the above-mentioned embodiment. This is because the native oxide film on the substrate 21 made of Si can be removed by the hydrofluoric acid vapor,
It is considered that the metal oxide film on the metal layer 24 cannot be removed by the hydrofluoric acid vapor, so that the difference in the growth rate of tungsten on the substrate 21 and the metal layer 24 becomes larger than that in the above-mentioned embodiment.

〔The invention's effect〕

According to the present invention, when forming a tungsten layer covering a contact hole, it is possible to make it difficult for a hollow to enter the tungsten layer. When the tungsten layer is etched and embedded in the contact hole, the substrate in the contact hole is etched. This is advantageous in that the device characteristics can be improved by making good contact in the contact hole.

[Brief description of the drawings]

1 and 2 are views for explaining one embodiment of a method for manufacturing a semiconductor device according to the present invention, FIG. 1 is a drawing for explaining a manufacturing process of one embodiment, and FIG. 2 is one embodiment. FIG. 3 is a diagram for explaining the manufacturing process of the conventional example, and FIG. 4 is a diagram for explaining the problems of the conventional example. 21 ... Substrate, 22 ... Insulating film, 23 ... Contact hole, 24 ... Metal layer, 25 ... Tungsten layer, 26 ... Wiring layer.

Claims (1)

(57) [Claims] 1. A step of forming an insulating film having a contact hole on a substrate, and a metal layer having a slower growth rate for tungsten than that of the substrate so as to cover the inside of the contact hole and the insulating film by a sputtering method. And a step of selectively etching the metal layer by anisotropic etching to expose the substrate in the contact hole and leaving the metal layer on the side wall of the insulating film in the contact hole. Forming a tungsten layer by chemical vapor deposition so as to cover the substrate and the metal layer exposed in the contact hole; and etching the tungsten layer on the metal layer other than the contact hole. Leaving the tungsten layer only in the contact hole, The method of manufacturing a semiconductor device which comprises a step of forming a wiring layer so as to take the tungsten layer and the contact left in.